M won't lug

Got an M with stock block and crank, high altitude pistons, propane head and intake, dennys distributor and modified carb with 806 venturie. Guy I bought it from said it had 11.5 to 1 compression, am running 110 fuel. Has 57 HP on dyno. Engine pulls good untile it has to lug then it,s done. Thinking maybe smaller venture, have stock M and a 2 stage from a dennys carb. Which would you try, or any other ideas? Thanks.
 
Put it back on a dyno and put a vacuum gauge on the intake. If the vacuum gauge falls below 1 inch you need a smaller venturi. You could even plumb it in so you can read it while pulling. Are you running stock RPMs?
 
I am doubting your problem is carburetor. Run a compression check. Check valve adjustment, as another said, mark timing marks and check with timing light to verify distributor advance is functional. Then hook to dyno and tune it out. Also: it has been my experience that high compression engines don't lug well at lower rpms. Don't pull heavy enough to pull the engine down or in to high of gear . Try to keep engine wrapped up. Peak power is made with engine opened up, not at idle
 
When it was dyno tuned valve lash was set on the tight side gained about 2 HP there. Carb and timing were also set on the dyno for max HP. It runs out of power in the 6000 lb always and depending on the track have run out of power in the 5500 lb and even in the 5000 lb. PTO is out right now so I can pull 4500 lb, can put back in at end of season. Could do the vacuum gauge and I have a advance timing light to check the distributor,
 
I talked to Lemmons and he said M's weren't really known as good luggers. But I pull against a super M that really hangs in there, and he pulls up to 6500 lbs. But he may have a 283 motor, don't know. Where I had mine tuned the said they've had M's with 450 engines that had 65 HP. Never heard off Paul, where is he located?
 
I would be looking at the cam in it. You told us on all that's done to it but the cam is a heart of any motor. Tell a good cam grinder guy what is done and he will get you a good cam for the power you want at the rpms you can run. If your cam is too far advance it will make good power at high rpms but fall on it face when it comes to luging. You are better to have the cam a little late in it this will make it lug better at lower rpms. I first would check out the cam it sounds like it is not right for that build of the motor.
 
I wound put a dial indicator on the lifter to see when the intake valve is starting to open to were the piston on compression is at. How old is the cam now it would be nice to put a degree wheel on it so when u fine top dead center on number one you can see what the valve are doing. A new fresh ground stock cam will be better because they improve them to run a lot better an power. Find out what your lift is to be with the cam and then with the dial indicator it will show how that cam is at.
 
Other M's probably 400 plus cu in. 100 plus hp.I have 80 hp. And will power out at 5000 lb. At a clay track. Like Princeton In.
 
you certainly don't need that big of a venturi in the carburetor for a stock M. it needs about thirty or forty more horsepower to spin out on a good track unless you have tires that won't pull at all.
 
give us horsepower readings at all the engine rpms from 400 up to 2200 and then using the formula HP=Torque in ft-lbs X rpm all divided by the number 5252 we can then plot out a graph of the torque over all the rpms and see where it falls on its face. A stock IH M camshaft is extremely poor. The intake duration is only about 168 degrees and the point of maximum lift for the intake valve is at 115 crankshaft degrees ATDC. So you can see that 115 minus 84 degrees means the intake valve isn't even getting to .050 inch lift to start opening until the crankshaft has turned 31 degrees ATDC. So, the piston has moved quite a ways down the intake stroke without the intake valve being open any for the air/fuel mixture to start to move into the cylinder. The stock intake lobe only displaces .270 inches at maximum lift. The rocker ratio stock I believe is 2:1. The exhaust duration is 182 degrees duration and is the same lift as the intake.

I have two reground camshafts for a M,superM, 400,450 that have .375 lift at the cam lobes and straighten out that very late intake timing by advancing the intake lobes relative to the end of the camshaft without moving the exhaust lobes. The duration of my lobes is 204 degrees which is still short for a slow running tractor engine and will thus lug good.
 
ground them with a friend in Indianapolis back in the mid-90s when I did all the JD two banger cams. The M was actually worse than the JD A,B,G,50,60,70 timing events. Have two M cams left over and I think one for a LP as it has left handed threads on the front. I'm thinking these are 43 percent more lift than stock M....you'd have to do the math to check that.
 

cvphoto35608.jpg
 
I can be contacted at my e-mail which is [email protected] or by entering that e-mail as one of your contacts on skype after you download the skype app. . The skype app. is free for folks to talk back and forth over like a phone conversation but you will need a microphone obviously .
 
WFE270 : Are those compression pressures you posted on the "M won't lug update" four different tests on the same cylinder or are the all four pressures when you tested each of the four cylinders ?????
 
(quoted from post at 17:14:00 09/08/19) WFE270 : Are those compression pressures you posted on the "M won't lug update" four different tests on the same cylinder or are the four pressures when you tested each of the four cylinders at one session ?????

because if those are the pressures of the four different cylinders at one testing session then you must answer the question why the one cylinder has so much more compression at CRANKING SPEED. I wouldn't run the engine or go pullling until you rule this scenario out ......that something has happened in the valvetrain that is causing that cylinder with the high pressure to act as if it is operating with a much shortened total duration on its intake lobe. If a cam has a shorter duration then it will have more compression pressure at cranking speed because the intake valve is effectively closing at an earlier time ABDC(after bottom dead center) on the compression stroke and so the piston moves up further after the valve is closed so the pressure is higher. So maybe you have a half wiped out intake lobe on that cylinder with pieces of it in the oil pan or a greatly bent intake push rod as you stated you ran a very greatly reduced valve lash looking for more power. Even if the valve lift were only .150 inches because of a damaged valve train, at only cranking speed the cylinder would still get completely full on the intake stroke at only cranking rpm because the piston speed is so slow. However, when the engine is running(dynamic compression) that cylinder would be very very weak even though it is still firing. It wouldn't miss but the tractor would be running on 3.2 cylinders and "would not lug"

Shouldn't the two differents threads on this same subject be combined into one by a moderator ?
 
(quoted from post at 15:26:15 09/10/19)
Too much ignition advance at low rpms?
Lean mixture ?
Over rich mixture?
Retarded cam timing .

Certainly is "Retarded cam timing" if everything in the valvetrain and timing gears is factory. The stock camshaft in a M,Super M,400, or 450 doesn't even take up all the tappet clearance and start to open the valve until the crank has turned 31 degrees after top dead center. Good idea thinking that advancing the timing gears one tooth because that would straighten out the late timing of the intake lobes....but problem is the exhaust lobes would then be opening way to early in the power stroke. Would sound awesome lugging on the dyno because that exhaust pressure would be much greater out the manifold but the dyno would show compromised hp and torque.
 

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